Support frame for color selection electrode in color picture tube

ABSTRACT

A color picture tube having a color selection electrode supported in a support frame disposed within the tube envelope consisting of a panel, a cone and a neck, said support frame consisting of an axial flange portion extending substantially parallel to the side wall of the panel, a radial flange portion extending inwardly from and at right angles to said axial flange portion and an electron shield flange portion extending rearwardly from the inner edge of said radial flange portion and substantially parallel to the path of electron beams directed to the edge of the color selection electrode. With this construction, excessively scanned electron beams are prevented from reaching the phosphor screen on the inner side of the face plate of the panel, thus improving the color purity of the reproduced picture.

United States Patent [1 1 Nagao, deceased Apr. 30, 1974 22 Filed:

' 211 App]. No.: 210,453

[ SUPPORT FRAME FOR COLOR SELECTION ELECTRODE lN COLOR PICTURE TUBE [75]Inventor: Tomohiro Nagao, deceased, late of Yokohama, Japan by lwaoNagao, heir [73] Assignee: Hitachi, Ltd., Marunouchi,

Chiyoda-ku, Japan Dec. 21, 1971 [52] US. Cl. 313/85 S, 3l3/92 B3,549,932 l2/l970 Lindeman... 313/85 S Primary Examiner-J1. K. SaalbachAssistant ExaminerSiegfried H. Grimm Attorney, Agent, or Firm-Craig &Antonelli ABSTRACT A color picture tube having a color selectionelectrode supported in a support frame disposed within the tube envelopeconsisting of a panel, a cone and a neck, said support frame consistingof an axial flange portion extending substantially parallel to the sidewall of the panel, a radial flange portion extending inwardly from andat right angles to said axial flange portion and an electron shieldflange portion extending rearwardly from the inner edge of said radialflange portion and substantially parallel to the path of electron beamsdirected to the edge of the color selection electrode. With thisconstruction, excessively scanned electron beams are prevented fromreaching the phosphor screen on the inner side of the face plate of thepanel, thus improving the color purity of the reproduced picture.

6 Claims, 6 Drawing Figures m mgmrnaomm 181381.492

SHEUIUFZ FIG, a PRICR ART PATENTEDAPR30 m4 My 2 F 2 3.8083192 F l 5 2PRIOR ART BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to color picture tubes and,

more particularly, to improvements in the construction of the colorselection electrode support frame for color picture tubes.

Description of the Prior Art The usual color picture tube has a colorselection electrode supported in a support frame which is disposedwithin the tube envelope consisting of a panel having a face plateprovided with an inner phosphor screen, a cone and a neck. The colorselection electrode support frame usually has an L-shaped crosssectional contour constituted by an axial flange portion extendingparallel to the tube axis and a radial flange portion inwardly extendingfrom the axial flange portion. The support frame is usually spaced a gapof about 1 to 2 cm from the side wall of the tube envelope panel. Thisgap is closed with an electron shield in order to prevent excessivelyscanned electron beams, i.e., electron beams excessively deflected outof the color selection electrode such as a shadow mask from entering theafore-said gap and reaching the phosphor screen on the inner side of theface plate of the panel, whereby the deterioration of color purity thatis likely to result in the edge portion of the reproduced picture on theface plate screen is prevented.

However, with the conventional color picture'tube part of the electronbeams reflected at the panel side wall or cone of the tube envelopecannot be prevented from penetrating the color selection electrode, forinstance small holes or pores of a shadow mask, and reaching thephosphor screen. Therefore, the color purity of the edgepart of thereproduced picture is deteriorated.

Meanwhile, in the operation of the color picture tube, as electrons shotfrom the electron guns strike the color selection electrode, theirkinetic energy is converted into heat energy, so that the temperature ofthe color selection electrode, such as a shadow mask, and its supportframe is elevated to cause considerable thermal expansion. Thedeformation of the color selection electrode and its support frame dueto thermal expansion thereof would cause color fringing and deterioratethe color purity of the reproduced color picture. To av- Another objectof the'invention is to provide a color picture tube, in which thedeformation of the color selection electrode and its support frame dueto thermal expansion thereof can be reduced to reduce the color fringingand improve the color purity.

BRIEF DESCRIPTION OF THE DRAWING The invention will now be described inconnection with the accompanying drawing, in which:

FIG. 1 is a sectional view, partly broken away, showing a usual colorpicture tube.

FIG. 2 is a fragmentary sectional view showing part of the tube of FIG.1.

oide this undesirable deformation due to thermal expansion, it is usualto blacken the color selection electrode support frame so that heatproduced by impingement of electrons upon the color selection electrodemay be radiated via the support frame thereof so as to hold the colorselection electrode and the support SUMMARY OF THE INVENTION An objectof the invention is to provide a color picture tube, which is capable ofeliminating undesired effects of excessively scanned electron beams andimproving the color purity of the reproduced picture.

showing other examples of the shadow mask frame for the color picturetube embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Presently, shadow mask typecolor picture tubes are the most popular of the color picture tubes, sothe following description of the preferred embodiment is concerned withshadow-mask type color picture tubes. However, it is to be understoodthat the invention is not limited to the shadow mask type color picturetubes, but it can also be applied to color picture tubes provided withsuch color selection electrodes as grids.

To facilitate the understanding of the invention, a typical prior-artcolor picture tube will now be described.

FIGS. 1 and.2 show a typical color picture tube, which has a glass tubeenvelope 11 consisting of panel 12, cone l3 and neck 14. The panel 12has a front face plate 12a provided with inner phosphor screen 15 and aside wall portion 12b extending parallel to the tube axis A A. Withinthe neck 14 is disposed an electron gun structure 16, which consists ofa plurality of electron guns assembled together. The electron gunstructure 16 is disposed.such that a plurality of electron beams (notshown) are shot from it toward the phosphor screen 15 on the inner sideof the face plate 12a. Between the electron gun structure 16 andphosphor screen 15 there is interposed a perforated shadow mask 17serving as a color selection electrode. It is supported in a shadow maskframe 18. The frame 18 holds the shadow mask 17 a suitable distanceapart from the phosphor screen 15, and it is fixed in position relativeto the panel 12 through a leaf spring 19.

The shadow mask frame 18 usually has an L-shaped cross sectionalprofile, consisting of an axial flange portion 18a extending parallel tothe tube axis A A and a radial flange portion 18b extending normal tothe tube axis A A. It is spaced from the outer side wall 12b of thepanel, and the gap between it and the panel, usually of l to 2 cm, isclosed with an electron shield 20 in contact with both of them. Theelectron shield 20 serves to prevent the electron beams from enteringthe gap between the shadow mask frame 18 and the panel side wall 12b.Thus, the electron beams will not enter the gap between the frame 18 andpanel side wall 12b at the time of the so-called excessive scanning atwhich the beams are deflected beyond the shadow mask 17.

With the color picture tube of the above construction, however, anelectron beam led along path B in FIG. 2 and reflected at the panel sidewall 12b or cone 13 is likely to pass through small holes or pores ofthe shadow mask 17 and strike the phosphor screen 15, thus adverselyaffecting the color purity of the edge area of the face plate 12a.

Also, in the operation of the color picture tube of the aboveconstruction about 80 to 85 percent of electrons shot from the electrongun structure 16 strike the shadow mask 17. Upon impingement ofelectrons upon the shadow mask, their kinetic energy is converted intoheat energy, so that the temperature of the shadow mask 17 is usuallyelevated to 70 to 100C. Such a high temperature of the shadow mask 17and its frame 18 can cause a considerable thermal expansion thereof. Thedeformation of the shadow mask 18 and its frame 18 due to this thermalexpansion would cause fringing of the color reproduction and deterioratethe color purity. To avoid the above undesired deformation, the shadowmask frame 18 is usually blackened for radiating heat through theblackened frame so as to eventually hold the shadow mask l7 and theframe 18 at a low temperature.

However, in the usual color picture tube of FIGS. 1 and 2, the electronshield 20 which is not blackened covers almost all the rear surface ofthe radial flange portion 18b of the shadow mask frame 18, greatlyhindering the heat radiation from the frame 18.

FIGS. 3 and 4 show preferred embodiments of the color picture tubeaccording to the invention. In these Figures, corresponding parts tothose in FIGS. 1 and 2 are designated by same reference numerals.

Referring to FIGS. 3 and 4, reference numeral designates a shadow maskframe, which consists of an axial flange portion 3011, a radial flangeportion 30b and an electron shield portion 30c. The axial flange portion30a extends substantially parallel to the panel side wall 12b, theradial flange portion 30b extends substantially perpendicular to theaxial flange portion 30a, and the electron shield portion 30c extendssubstantially parallel to the path C of electron beam directed to theedge of the shadow mask 17.

In the embodiment of FIG. 3, the radial flange portion 30b extends fromthe end of the axial flange portion 30a nearer to the electron gunstructure, with shadow mask 17 secured to the axial flange portion 30aand electron shield 20 to the radial flange portion 30b of the frame 30by suitable securing means.

In the embodiment of FIG. 4, the radial flange portion 30b extends fromthe end of the axial flange portion 30a nearer to the phosphor screen15, with both shadow mask 17 and electron shield 20 secured to the axialflange portion 300 of the frame 30 by suitable securing means.

In the color picture tubes having a shadow mask frame 30 of the aboveconstructions, even if there are electron beams led along path D andreflected at panel side wall 12b or cone 13 of the tube envelope, thereflected electron beams will be interrupted by the electron shieldflange portion 30c which extends substantially parallel to the electronbeam path reaching the edge of the shadow mask 17, so that the reflectedelectron beams will not reach the shadow mask 17. Thus, deterioration ofcolor purity which is otherwise likely to result in the edge area of theface plate 12a can be completely prevented.

Also, even if one of the axial, radial and electron shield flangeportions 30a, 30b and 30c of the shadow mask frame 30 is completelycovered with the electron shield 20, the effective heat radiation areacan be readily increased compared to the prior-art shadow mask frame ofthe L-shaped cross sectional profile shown in FIGS. 1 and 2. Thus, heatradiation can be increased, so that the frame 30 can eventually be heldat a lower temperature to reduce deformation of the shadow mask 17 dueto the thermal expansion of the shadow mask frame 30 so as to reduce oreliminate the fringing of color reproduction and deterioration of thecolor purity.

FIGS. 5a and 5b show modifications of the shadow mask frames 30 shown inFIGS. 3 and 4. In these modiflcations, the electron shield flangeportion 30c of the frame 30 is made progressively thinner toward therear edge 30d. With this construction, the electrons striking the edge30d of the flange portion 30c can be reduced compared to the precedingembodiments of FIGS. 3 and 4, in which the electron shield portion 30cof the frame 30 has a unifonn thickness. In these modifications theeffective heat radiation area can be substantially the same as or ratherlarger than that in the preceding embodiments of FIGS. 3 and 4.

As has been described in the foregoing, with the color picture tubeaccording to the invention it is possible to prevent electron beamsreflected at the panel side wall or cone of the tube envelope fromreaching the shadow mask and to greatly increase heat radiation from theshadow mask frame.

I claim:

I. A color picture tube comprising a glass tube envelope consisting of apanel portion, a cone portion, and a neck portion, a phosphor screenprovided on the inner side of a face plate of said panel portion, anelectron gun structure disposed within said neck portion of said tubeenvelope for directing electron beams to said phosphor screen, a colorselection electrode interposed between said phosphor screen and saidelectron gun structure and including a plurality of apertures throughwhich said electron beams pass to said phosphor screen, support meansfor holding said color selection electrode in position in said tubeenvelope including an annular electrode support spaced from the sidewall of said panel portion so that an annular gap is formedtherebetween, said electrode support consisting of an axial flangeportion extending substantially parallel to the side wall of said panelportion, a radial flange portion extending inwardly from and at rightangles with respect to said axial flange portion and a protrusive flangeportion extending rearwardly from the inner edge of said radial flangeportion toward said electron gun structure, the inner surface of saidprotrusive flange portion facing the tube axis being substantially inparallel to the path of electron beams directed from said electron gunstructure to the edge of said color selection electrode, and an annularelectron shield extending radially outward from said electrode supporttoward said side wall of said panel portion to close said annular gap.

2. The color picture tube according to claim 1, wherein said radialflange portion extends from the end of said axial flange portion nearerto said electron gun structure.

3. The color picture tube according to claim 2, wherein the thickness ofsaid protrusive flange portion is progressively reduced toward its endnearer to said electron gun structure.

4. The color picture tube according to claim 2, wherein said radialflange portion extends from the end of said axial flange portion nearerto said phosphor screen.

5. The color picture tube according to claim 4, wherein the thickness ofsaid protrusive flange portion is progressively reduced toward its endnearer to said electron gun structure.

6. A color picture tube comprising a glass tube envelope consisting of apanel, a cone and a neck, a phosphor screen provided on the inner sideof a face plate of said panel, an electron gun structure disposed withinsaid neck, a color selection electrode interposed between said phosphorscreen and said electron gun structure, and an electrode support to holdsaid color selection electrode in position, said electrode supportconsisting of an axial flange portion extending substantially parallelto the side wall of said panel, a raidal flange portion extendinginwardly from and at right angle's with respect to said axial flangeportion and a protrusive flange portion extending rearwardly from theinner edge of said radial flange portion, the inner surface of saidprotrusive flange portion facing the tube axis being substantiallyparallel to the path of electron beams directed from said electron gunstructure to the edge of said color selection electrode, said protrusiveflange portion being progressively reduced in the thickness toward itsend nearer to said electron gun structure.

1. A color picture tube comprising a glass tube envelope consisting of apanel portion, a cone portion, and a neck portion, a phosphor screenprovided on the inner side of a face plate of said panel portion, anelectron gun structure disposed within said neck portion of said tubeenvelope for directing electron beams to said phosphor screen, a colorselection electrode interposed between said phosphor screen and saidelectron gun structure and including a plurality of apertures throughwhich said electron beams pass to said phosphor screen, support meansfor holding said color selection electrode in position in said tubeenvelope including an annular electrode support spaced from the sidewall of said panel portion so that an annular gap is formedtherebetween, said electrode support consisting of an axial flangeportion extending substantially parallel to the side wall of said panelportion, a radial flange portion extending inwardly from and at rightangles with respect to said axial flange portion and a protrusive flangeportion extending rearwardly from the inner edge of said radial flangeportion toward said electron gun structure, the inner surface of saidprotrusive flange portion facing the tube axis being substantially inparallel to the path of electron beams directed from said electron gunstructure to the edge of said color selection electrode, and an annularelectron shield extending radially outward from said electrode supporttoward said side wall of said panel portion to close said annular gap.2. The color picture tube according to claim 1, wherein said radialflange portion extends from the end of said axial flange portion nearerto said electron gun structure.
 3. The color picture tube according toclaim 2, wherein the thickness of said protrusive flange portion isprogressively reduced toward its end nearer to said electron gunstructure.
 4. The color picture tube according to claim 2, wherein saidradial flange portion extends from the end of said axial flange portionnearer to said phosphor screen.
 5. The color picture tube according toclaim 4, wherein the thickness of said protrusive flange portion isprogressively reduced toward its end nearer to said electron gunstructure.
 6. A color picture tube comprising a glass tube envelopeconsisting of a panel, a cone and a neck, a phosphor screen provided onthe inner side of a face plate of said panel, an electron gun structuredisposed within said neck, a color selection electrode interposedbetween said phosphor screen and said electron gun structure, and anelectrode support to hold said color selection electrode in position,said electrode support consisting of an axial flange portion extendingsubstantially parallel to the side wall of said panel, a raidal flangeportion extending inwardly from and at right angles with respect to saidaxial flange portion and a protrusive flange portion extendingrearwardly from the inner edge of said radial flange portion, the innersurface of said protrusive flange portion facing the tube axis beingsubstantially parallel to the Path of electron beams directed from saidelectron gun structure to the edge of said color selection electrode,said protrusive flange portion being progressively reduced in thethickness toward its end nearer to said electron gun structure.